The invention relates to a motor vehicle seat supported so as to be able to vibrate by means of a mechanical vibration system and a pneumatic spring having the characteristic features of the preamble of claim 1 for holding the static height of the motor vehicle seat constant independently of the weight of the respective seat occupant.
Motor vehicle seats of this type are known from DE 27 53 105 C2 filed by the applicant. They operate with a control cam whose end-side trigger cams mount the valve plunger of an aerating valve dependent on the vibration travel when the vibration travel of the vibration system exceeds a level deemed acceptable above or below the motor vehicle seat""s static height to be held constant. The air pressure in the pneumatic spring decreases or increases accordingly. When the respective vibration travel reverses its motion and shortly before reaching the static height to be held constant the respective open valve is closed again in that the trigger cam of the control cam is pulled down again from the valve plunger by the trigger cam.
In order to achieve such varying distances between the vibration travel switch positions and the constant static height when opening and closing the valves,the motor vehicle seat known in the art operates with a so-called trailing control cam, where a driving pin mounted on a rod of the scissors-type rod vibration system first has to pass a certain trailing distance in a trailing distance recess of the control cam after the respective vibration has reversed its motion until it stops at the end of the trailing distance recess and is able to pull down the trigger cam of the control cam from the valve plunger of the valve.
The invention is based on the above state of the art. One objective of this invention is to reduce the problems of noise and wear related to this kind of trailing control system.
Also, previously the seats always had the disadvantage that the seats were able to freely vibrate upward from the respectively set static height up to the limit stop. This means that the upper part of the seat, including the driver, is able to vibrate up to said upper limit stop, for example when the driver gets up. With a height adjustment range of 100 mm, for example, and a vibration travel of +/xe2x88x9240 mm, for example, this could mean an upward vibration of up to 140 mm in the lowest height adjustment position. One potential consequence is that the driver is hampered when he exits the vehicle.
Therefore, another objective of the invention is to provide a motor vehicle seat in which the maximum vibration is adjustable so as to prevent the above disadvantages.
Noise problems in the known trailing control systems are primarily caused by the driving pin mounted on the vibration system striking the ends of the trailing distance recess of the control cam and also by the trigger cams of the control cam striking the plunger of the valves before they are able to mount said valve plungers. Said striking noises intensify as the trailing control cam gets dirtier and thus moves more sluggishly.
The problems of wear in the known trailing control cams are primarily related to the trigger cams of the control cam and the valve plungers of the valves and have increased in recent years because the on-board compressed air systems of the motor vehicles which also supply compressed air to the pneumatic spring of the motor vehicle seat increasingly operate at a higher pressure level.
To solve the problem of reducing noise and wear in trailing control systems it is proposed in accordance with the invention to omit in a motor vehicle seat operating according to the method of DE 27 53 105 C2 for holding the static height constant the above mechanical trailing control cam with said valves and instead using valves and a control system which are characterized in that the valves each have a stopping device (for example in the form of a cylinder piston, a ball, or the like), which lifts off of its valve seat for opening the valve against the force of a closing spring, where the stopping device consists of a ferromagnetic material and is disposed in a plastic valve housing and where the control system for opening the valves consists of a control lever or a control carriage with a permanent magnet that approaches the stopping device of the aerating valve non-contacting dependent on the vibration travel in such a way that the respective stopping device in the open valve position has a distance from the permanent magnet which is shorter, yet non-contacting, by the lifting motion of the stopping device from its valve seat.
The inventive solution offers considerable advantages.
For one, by using a permanent magnet positioned in a pivoting control lever or a shifting control carriage the stopping device of an aerating valve or a deaerating valve can be actuated without requiring any mechanical contact between said components for this purpose.
Thus, the problem of wear between said components is prevented. The proposal of installing a permanent magnet in the control lever or control carriage suggests itself because no power supply lines have to be installed in the moving parts as would be the case if a similarly acting magnetic field were to be provided by means of current-carrying electrical conductors, which is also feasible, in principle.
The strength of the magnetic field is not affected by a valve housing, which, according to the theory of the invention, consists of plastic, but it is affected by the ferromagnetic material of which the stopping devices of the valves have to be made. Said materials provide a considerable field-strengthening effect for the magnetic field. The magnetic field acts as a pulling force both on the opposite pole surfaces of the permanent magnet and on the respective stopping device, which force also depends, among others, on the distance between the permanent magnet and the stopping device.
The above physical facts are employed by the theory of the invention in that in the open valve position the respective stopping device has a distance from the permanent magnet which is shorter by the lifting motion of the stopping device from its valve seat. Then the magnetic attractive powers are higher with the result that the valve will be held longer in its open position when the control lever or control carriage with the permanent magnet is moved away from the stopping device of the valve dependent on the vibration travel. In other words, the point in time of closing the valve xe2x80x9ctrailsxe2x80x9d relative to the motion of the permanent magnet which is controlled by the vibration travel similar to the state of the art with the mechanical trailing control cam, but having the very substantial advantage that said trailing process in accordance with the theory of the invention is now non-contacting and thus results in less wear and less noise.
An especially suitable practical embodiment of the invention is proposed which is characterized in that both valves (aerating valve and deaerating valve) are housed in a common plastic valve housing (as is basically known in the art) and that they are oriented relative to each other such that their respective stopping devices perform lifting motions off of their respective valve seats which are parallel and oriented in the same direction. The common plastic valve housing is intended to largely hermetically seal the valve parts against external effects, pollution and the like, and the permanent magnet should be mounted on a pivoted lever which is disposed so as to pivot on an external wall surface of the valve housing and, in dependence of the vibration travel, causes the permanent magnet on the external wall surface of the valve housing and transversely to the lifting motions of the stopping devices to approach the respective stopping devices such that in the final stage of approaching the pole surface of the permanent magnet is plane-parallel opposite and at a distance of the preferably plane bottom area of the stopping device.
With the inventive solution of holding the static height of a motor vehicle seat constant an integrated height adjustment for the vibration system can be combined easily and cost-effectively, which, in accordance with claim 3 of this invention, is characterized in that the valve housing is mounted so as to turn about an axis at the crossing point of a scissors-type rod vibrating system and that the precise turning position of the valve housing can be adjusted and set by means of a Bowden cable mounted on the scissors-type rod and on the valve housing, which can be tension and/or pressure loaded. It is also preferable that the turning position of the valve housing is electrically adjustable, preferably by means of a servomotor which is actuated by means of a potentiometer, for example. This advantageously also allows the implementation of memory effects in the seat, i.e. pre-defined seat parameters can be stored and recalled.
The second objective of this invention, namely providing a motor vehicle seat where the maximum seat vibration is adjustable, is achieved in accordance with the invention based on the associated claim 4. Advantageous embodiments are provided in the respective sub-claims.
Accordingly, this invention provides a motor vehicle seat with an integrated static height adjustment mechanism comprising a control system with which a constant maximum vibration of the motor vehicle seat is adjustable automatically and simultaneously with the static height adjustment.
Said control system corresponds to a traveling height limit stop and ensures a constant maximum seat vibration at any height position or a constant free seat vibration travel upward or downward or especially preferably both upward and downward. This means that regardless of the height position at which the motor vehicle seat is set a determinable constant seat vibration from said height position setting van be adjusted or controlled by means of the control system. This prevents the motor vehicle seat from being able to vibrate freely upward or downward from the set height position to the limit stop and thus could hamper the driver, for example in exiting the vehicle. The traveling height limit stop ensures that while the motor vehicle seat provides a certain comfortable springiness for the driver, which is necessary, for example when passing over an uneven surface or a bump in the road, it also prevents the vibration coupled with the suspension from being so strong that it is uncomfortable or inconvenient for the driver.
In a preferred embodiment of the seat of the invention the control system has at least an eccenter and a catch lever where the eccenter and catch lever are movable relative to each other dependent on the seat vibration up to a certain limit stop position and interact such that a constant maximum seat vibration is adjustable simultaneously and automatically with every height position adjustment. Especially preferably the maximum absolute vibration path is defined by the constant maximum vibration path via the height setting.
The eccenter is equivalent to a circular disk, preferably a circular disk whose circumference has a toothed surface, at least in part. Said circular disk is positioned outside the center of the circle. It is preferably disposed so as to turn at the center bearing point of the seat""s vibration system. A toothed ring is preferably disposed on the eccenter which is also disposed so as to turn in the center bearing point and which is firmly connected with the eccenter.
The catch lever is disposed so as to move between the inside and outside scissors of the seat""s vibration system and it preferably also has a toothed surface, at least in part.
In the home position of the motor vehicle seat the eccenter and the catch lever have a certain adjustable distance from each other where advantageously the respective toothed areas on the eccenter and the catch lever are opposite.
When the vibration system of the motor vehicle seat springs upward, for example, because of a bump in the road, for example,a relative motion between the catch lever and the eccenter takes place. When the motor vehicle seat vibrates the angle between the inside and outside scissors of the seat""s vibration system changes, i.e. when the motor vehicle seat vibrates upward the angle becomes larger accompanied by a motion of the catch lever disposed on the inside and outside scissors in the direction toward the eccenter. This means that as the vibration of the motor vehicle seat from its home position increases the angle between the inside and outside scissors of the seat""s vibration system continues to increase and consequently the distance between the catch lever and the eccenter decreases accordingly. At a certain vibration level a limit stop position is reached at which the catch lever and the eccenter meet, preferably with their respective toothed areas, and thus stop the motor vehicle seat from vibrating further.
In order to change the static height adjustment of the vibration system while holding the maximum seat vibration constant, the eccenter on the center bearing point is radially adjusted simultaneously and automatically with the static height adjustment such that this results in another stop limit, which is adapted to the respective height adjustment, on the toothed eccenter area so that the distance between the catch lever and the eccenter, and thus the maximum vibration, remain constant. This means that the same maximum vibration and the same free upward vibration path have been realized for every height position adjustment. In other words, the adjustment of the motor vehicle seat""s static height corresponds to a respective adjutment of the angle between the inside and outsides scissors of the seat""s vibration system. As explained above, however, this is accompanied by a motion of the catch lever disposed thereon relative to the eccenter, which means that the distance between the catch lever and the eccenter would initially be changed. In order to ensure a constant height limit stop, however, the distance between the catch lever and the eccenter has to be the same at every height position of the seat. This is achieved by the invention in that the eccenter is turned in accordance with the relative motion of the catch lever at every new height position adjustment such that the distance between the catch lever and the eccenter remains constant. This is made possible by positioning the eccenter outside the center of the circle.
In a preferred embodiment of the motor vehicle seat the automatic and simultaneous adjustment of the eccenter relative to each new static height adjustment of the motor vehicle seat is made by means of a gear, preferably by means of a two-stage gear.
The two-stage gear preferably consists of a first tooth lever and a second tooth lever. The first tooth lever is preferably firmly connected with the air valve, which is also disposed so as to turn on the center bearing point. The second tooth lever is disposed so as to turn on the inside scissors. The latter serve for the necessary transmission of the varying rotational angle between the air valve and the eccenter when the static height is adjusted. Therefore, the second tooth lever has two toothed rings disposed one above the other and firmly connected, where the diameter of the toothed rings is selected based on the desired or required transmission. The eccenter, the first and second toothed levers are disposed relative to each other such that the toothed ring of the first tooth lever engages in one of the two toothed rings of the second tooth lever while the toothed ring disposed on the eccenter engages in the other of the two toothed rings of the second toothed lever.
As explained above, every time the height of the motor vehicle seat is adjusted the angle between the inside and outside scissors of the vibrating system changes accordingly as a result of a change in the position of the height adjustment valve.
This is accompanied by a turn of the first tooth lever on which the Bowden cable also engages. Because of the interlocking, said turn of the first tooth lever causes the second tooth lever to turn which, again because of the respective engaging tooth rings, causes the eccenter to turn. The necessary transmission is determined by selecting the tooth ring diameters, namely the angle about which the eccenter has to be turned so that the distance between the eccenter and the catch lever remains constant at a certain height adjustment.
The valve setting angle is preferably between 15xc2x0 and 50xc2x0, especially preferably between 30 and 40xc2x0, particularly preferably between 33 and 37xc2x0. The setting angle of the tooth lever 2 is preferably between 50 and 140xc2x0, preferably between 70 and 110xc2x0, especially preferably 90xc2x0, and the setting angle of the eccenter is preferably between 100 and 210xc2x0, especially preferably between 130 and 190xc2x0, particularly preferably between 165 and 175xc2x0. The ratio between the valve and the eccenter thus achieved is defined by the preselected setting angles and is especially preferably approx. 1:4.7.